You can put one address into the TO: space and put all of the others into the BCC: space and the addresses in the BCC space will not show only the TO will show. So I have usually address the TO to myself when I do this.

If you want to get more fancy you can get Mozilla Thunderbird and the Mass malling ad on to the program and you will be able to have it create a separatly addressed email for each list member. You can also use msword to create a mass mail from a list giving you separately addressed emails but I have only used Thunderbird for this.